Optical Quality of the Cornea After Orthokeratology Based on Total Corneal Refractive Power, Corneal Asphericity, and Epithelial Thickness: Protocol for a Prospective Quasi-Experimental Pre-Post Study

Abstract

Abstract Background Orthokeratology is a nonsurgical corneal reshaping technique used for the temporary correction of myopia and for myopia control. Nighttime use induces central epithelial thinning and midperipheral thickening, altering corneal asphericity and higher-order aberrations. Objective The primary objective is to determine the change in anterior corneal spherical aberration after 1 month of orthokeratology use. Secondary objectives include evaluating changes in total corneal refractive power, the Q value, and epithelial thickness. Methods This prospective quasi-experimental pre-post study was conducted at a private ophthalmology clinic (Licari Vision Clinic, Tarragona, Spain). Participants were patients aged 8 to 21 years with myopia ranging from −1.00 to −5.00 D who underwent nighttime orthokeratology for 1 month. Outcome measurements included Pentacam tomography, anterior segment optical coherence tomography (OCT), and Zernike analysis, all performed in the morning 1 to 3 hours after lens removal. Cycloplegic refraction was performed at baseline only to confirm eligibility criteria and inform orthokeratology lens design. A minimum of 23 participants was required to detect a change of ≥0.14 μm in anterior corneal spherical aberration (α=.05; β=.05; power=95%; SD 0.166 μm), incorporating a 20% dropout rate. The unit of analysis will be the eye, including both eyes of each participant. To account for the nonindependence of contralateral eyes in the same participant’s within-subject repeated measurements, the primary and secondary outcomes will be analyzed using linear mixed-effects models with a fixed effect for time (baseline vs 1 month) and a random intercept for each participant. A significance level of P<.05 will be applied in all cases. Results The protocol received a favorable ethics opinion from the Drug Research Ethics Committee (Comité de Ética de la Investigación con medicamentos [CEIm]) of the Pere Virgili Institute for Health Research (Institut d'Investigació Sanitària Pere Virgili [IISPV]) in October 2024 (CEIm Code 159/2024) and was registered at ClinicalTrials.gov (NCT06775509). This study received no external funding. Recruitment was completed. Data collection has been finalized, and data analysis is currently underway. The study findings are expected to be published in January 2027. Conclusions Corneal optical quality may be modified after 1 month of orthokeratology lens use, and the findings may contribute to refining clinical decision-making regarding the use of orthokeratology for myopia management.